Events that'd make me drop this: if the male lead starts seeing his 'sister' in a romantic...

Spoiler alert
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ML already knew they are not siblings thus he did not see FL as a sibling from the very start. And u have to remember that in their house, sibling=enemy so no precious feelings abt sibs =^_^= he’s just keeping FL close/cherishing her bcos he needs to sacrifice someone precious to him for a ritual later on. Sooo theres that

;OO since when??? from the start??

yesss iirc reading the spoiler forum on novelupdates

This was shown somewhere in the beginning chapters as FL explains the origin of her birth. Ditri confirmed by saying her real mothers name or something to her when she was a baby. It was like “ahh so she’s the child of XXX.” I can’t fully remember the exact conversation but he does say that it’s a different woman than his birth mother here.

and i oop- damn im glad he knew from the beginning. it makes thing so much more simple

Yeah lol this plot device is overused in my opinion since I feel like this isn’t the moral norm (loving a sibling in any capacity beyond family. Even without blood relation). I mean authors can do what they want, but the device rarely ever goes well with people

Hmm yeah well, I usually just disregard morals when I read comics. I can hate a villain for doing something calling them evil and all but I'll read a comic with a completely fucked up mc who's doing the same or worse and love them. Since it's very hypocritical I just don't give a fuck and try not to overthink anythingヾ(❀╹◡╹)ﾉ~

LOL I get that. I just think this trope in particular is one that’s hard to navigate. The idea of loving your sibling clearly doesn’t bode well for many lolol and It unfortunately ends up taking over the entire story, even if romance isn’t the main focus